Won't run unless pedal to the floor. EGR?

[Scout23]

I have an 1986 Tercel with a 3AC. Recent head gasket replacement and was running fine. Over a few weeks my Tercel started idling a few hundred rpm back and forth when coming to a intersection when you stop. Now my Tercel won't stay running unless you throttle the pedal after it's been warmed up for about 5 minutes. During that five minute warm up you have to keep the pedal to the floor to keep the vehicle running and after about five minutes it will start to run "normal" but not well enough to be reliable to drive. It's dangerous to drive. It's not miss firing just surging or won't stay running. Also during this warm up period it is as if the car has no power or is being choked out. The automatic choke is working as it always has. I replaced the auxiliary acceleration pump diaphragm installed a new fuel filter, changed out any loose or bad vacuum lines. I pulled the carb off and took it apart but I didn't see anything out of the ordinary so I just put it back together. I'm thinking it's possibly the EGR valve? Any thoughts or ideas. I need to get my Tercel back on the road. Thanks in advance for any help. I've been reading tons and tons of repair info on here just didn't see one exactly like this.

[dlb]

the EGR only operates when the engine is warm, and then only at partial throttle, so i don't think it would affect the performance throughout the entire range, both hot and cold. you can disconnect and plug it if you want to test it though.

it sounds to me like there is a big vacuum leak. could there be a vac line that you have overlooked? i believe there's a big one just underneath the air filter housing which is a little tricky to reattach when putting the housing back on. i've found that one disconnected and causing poor running on tercs before. also, how's your air filter?

[Petros]

sounds like a vac leak to me. after you check the vac lines check for leak around the intake manifold, sometimes the temp cycling on the head will loosen the manifold nuts and bolts. just tighten them up.

the rpm cycling is a classic symptom of a vac leak. only one other problem will cause that beside a vac leak, internal problem in one of the carb system.

good luck.

[dlb]

in addition to obvious leaks, there are less obvious ones. i just remembered i posted a thread on them a while back. might be worth a read.

https://tercel4wd.com/forums/viewtopic.php?f=7&t=8058

also, if you search the forum for "cycling" or "dreaded cycling" you'll find a few more threads that may be pertinent to you.

[celtglen]

I would also pull the spark plugs -- they tell a mighty story about what is happening inside yer engine...

CG

[Scout23]

For future reference it turns out the lower timing gear and woodruff key were broken and I believe sometimes turning as the should but not always. This made the timing jump and was the cause of all my problems. Put a new lower timing gear and a 5mm woodruff key sanded down just a touch for a tight fit and the car runs like a top now. Should have looked at it sooner just didn't think it was the timing belt or gear as the individual I bought the vehicle from had said he had recently changed it. Problem was he used a 5/16 woodruff key instead of a 5mm and it eventually broke. Surprised it ran at all. Hope I didn't damage anything trying to get it running when the timing was off. I did pull the EGR off and it was plugged. Cleaned it up as best I could with some tools from Harbor Frieght and put it back on with new hoses and a carb rebuild but it was the timing gear causing the problems.

Thanks for all the help everyone provided.

[Petros]

that is a pretty rare problem, a woodruff key failure. I wonder why the original was replaced, lost perhaps. sounds like sloppy work by the PO (or the PO's mechanic). good find.

[rer233]

had a similar problem with my former GF's '84 fwd wagon. we'd already split up, and the LAST thing she was going to do is call me about a car problem. long story short, after unsucessfully spending a whole bunch of money trying to fix her lack of power problem she had her neighbor drive her to the local Car Max and she bought an escort wagon (yeech.) after that, she asked me if i wanted the tercel. i went and looked at it (any regulars on this site know how NUTS i am about these cars- especially since this was the first one i bought.) anyway, the thing ran like crap, and made a noise that sounded EXACTLY like a rod knock. when i got it home and checked it out, turned out the crankshaft pulley bolt was loose. put a new/used balancer, crank puley, woodruff key and lots of loctite on the crank, and the engine's still running today (45 k miles later.)

[marlinh]

I hope this works. This is a picture of a crank gear that must have been loose for years. The fellow who was driving this car was stranded on the side of the road. The car ran like crap, and intermittently would run better. The timing was all over the place and the engine had quite the rattle.

[dlb]

what's that chunk at the bottom of the pic, marlinh? was it supposed to sit in the carved out notch in the crank gear?

[marlinh]

Yes, that was the key way. It took quite a bit to get it out of the crankshaft. The groove it wore in the pulley was remarkable. It had to be loose for such a long time to create that wear. Needless to say that car was pretty gutless when it ran at all.

[rer233]

looks REAL familiar- bet the crankshaft's a little busted up too, huh. good luck!

[marlinh]

Miraculously there was no damage to the crankshaft.